This invention is broadly concerned with ceramic oxide powders and their method of preparation. More particularly, it is concerned with the formation of ceramic oxide powders obtained using a flame process and which have well characterized size distribution, shape, purity, morphology, and crystalline form.
Ceramic oxides and mixtures thereof find utility as catalysts, ceramics, optical fibers, pigments, and superconductors. More specifically, oxide powders such as TiO.sub.2 (titania) and SiO.sub.2 (silica) are used in industry to produce paint opacifiers, catalysts, catalyst supports, ceramic membranes, fiber optics, liquid thickeners, varistors, capacitors, etc. Successful manufacture of these products, however, depends on controlling the properties of the starting powders. The properties of the powder strongly depend on the method of powder synthesis. Most titania powder is produced using the chloride process.
Mixed ceramic oxide powders such as, for example, SiO.sub.2 --Al.sub.2 O.sub.3, Al.sub.2 O.sub.3 --TiO.sub.2, TiO.sub.2 --V.sub.2 O.sub.5, SiO.sub.2 --TiO.sub.2, SiO.sub.2 --GeO.sub.2 and Y--Ba--Cu--O, are used to produce catalysts, catalyst supports, ceramics, optical fibers, pigments, and superconductors. The degree of mixing of these ceramic oxides and their microstructures are critical to their reactivity, strength, refractivity, and electrical resistivity.
Mixed ceramic oxides may be simple mixtures thereof, agglomerates, one ceramic oxide supported on another, or one ceramic oxide coated with another. The ceramic oxide may also be a compound formed from two different ceramic oxides, e.g., Al.sub.2 O.sub.3. TiO.sub.2. Mixed ceramic oxides are typically prepared by flame spraying mixed sols thereof or by coating a ceramic oxide by depositing it from a solution such as an aqueous silicate solution. These methods are characterized by difficulty in controlling the properties of the mixed ceramic oxide obtained.